The prior art is generally cognizant of methods for inserting catheters into the blood stream of patients involving the insertion of the catheter into the patient while the catheter is carried over a hollow needle, or a trocar. One example of a device utilizing such a method for inserting a catheter into a patient is shown in U.S. Pat. No. 3,714,945, which describes a device suitable for inserting a semi-rigid catheter into the blood stream of the patient. It is generally a problem with all prior art semi-rigid catheter devices, and the apparatus for inserting such catheters, in that the catheters eventually cause a fibrin build-up in the blood vessel into which they are inserted. It has not generally been practicable to introduce more flexible catheters into a blood vessel.